Weathering, Erosion, & Deposition

Remember: Weathering is… the breaking down of rocks There are two types of weathering: mechanical weathering & chemical weathering. Weathering happens to rocks that are NOT MOVING. These rocks have been blasted by wind and sand causing them to become rounded. ABRASION

Erosion is the process by which weathered rock and soil are moved  from one place to another. Erosion carves the Earth's surface creating canyons, gorges, and even beaches. There are 4 agents of erosion: gravity water wind glaciers

Deposition is the process by which sediments (small particles of rock) are laid down in new locations. Deposition builds new landforms AND changes the shape of the land. Water is usually responsible for deposition but landslides can be caused by earthquakes and volcanoes.

Water as an Erosion Agent can erode great amounts of sediment (broken pieces of rock) Ex. Waves carry weathered rock from cliffs & deposit it as new sand on beaches. Ex. Rain carries sediment into rivers & streams

Weathering, Erosion, & Deposition These 3 work together in a continuous cycle that BOTH wears down & builds up Earth’s surface. Forces that build up Earth’s surface are called constructive forces. Forces that tear/wear down Earth’s surface are called destructive forces. Sometimes erosion & deposition work slowly, other times like in a thunderstorm or a flood they work quickly. These 3 are NEVER ENDING!

Erosion The main thing that causes erosion is water. In this picture the running water eroded the sides of this canyon and created the V-shaped valleys.

Mass Movement… Is one of several processes by which gravity moves sediment (pieces of rock) downhill. Mass movement can be SLOW or FAST. Gravity causes mass movement. Gravity moves rock & other materials down hill! 4 types of mass movement (landslide, mudslide, slump, & creep)

Landslides Are the MOST destructive kind of mass movement. Landslides- are when rock & soil slide quickly down a slope. Landslides are common where roads have been cut through hills or mountains.

Mudslides are fast, downhill movement of a mixture of water, rock, & soil. Mudslides often happen after heavy rains.

Slump Mass movement in which a “mass” of rock & soil suddenly slip down a slope in 1 big motion or mass. Slump can look like a giant spoon has started to scoop a mass of soil & rock out from a hillside.

Creep Is a very slow downhill movement of rock & soil. Creeps are so slow, that you will hardly notice it, but you can see the effects of creeps in telephone poles, gravestones, mail box posts, & fenceposts.

Creep

Landslide, Mudslide, Slump, or Creep?

Landslide, Mudslide, Slump, or Creep?

Landslide, Mudslide, Slump, or Creep?

Landslide, Mudslide, Slump, or Creep?

Landslide, Mudslide, Slump, or Creep?

Erosion The first five pictures of this presentation are of the same rock, just in different time periods. Pay attention to the dates on the side of the pictures and see what the water did to this rock. 1890

Still the same rock. 1910

Still the same rock 1920

Still the same rock. 1970

Still the same rock, but where did it go? 1990

Here is another picture of what erosion caused.

The ground has been washed away by water. That’s erosion.

Critical Thinking ??? Why is weathering so important to life on land? Explain why water erodes Earth’s surface more than wind does? What are ways in which people cause erosion? What can we do to prevent erosion?